The proposed research has the primary objective of investigating the transport and deposition of hygroscopic aerosols in the human respiratory tract, using physical models of the larynx and tracheobronchial tree. Emphasis will be placed on deposition in the larynx and the airways with partial obstruction, which arises in patients with various types of lung diseases. The study will be both experimental and theoretical in nature. In the experimental part, physical models of the larynx and tracheobronchial tree will be used to investigate the effects of particle size, chemical composition of the particles, and airflow on deposition. A cam-driven piston-type breathing machine will be used to simulate the respiratory flow of patients with airway diseases. In the theoretical study, the problems of flow and deposition in well-defined passageways corresponding to the larynx and the partially obstructed airways will be investigated. The study represents a continuation of our research on inhaled particles. The long-term objective is to develop a mathematical model for predcting the local and total deposition of hygroscopic particles in the human airways. The predictive model should have application in aerosol therapy.